Method of manufacturing a sealing device

ABSTRACT

A sealing device to be mounted between a member and a rotation shaft which can be rotated relatively to the member, includes an annular flanged portion formed of a resin and disposed to surround the rotation shaft, and extends in a radial direction of the rotation shaft. A resin seal lip extends from an inner end of the flanged portion in an axial direction of the rotation shaft toward fluid to be sealed in such a manner that the resin seal lip surrounds the rotation shaft. The resin seal lip has a first seal ring having a sealing surface which hermetically and slidably contacts the rotation shaft, a second seal ring having an elastic flanged portion formed of a rubber material and disposed to surround the rotation shaft and extending in a radial direction of the rotation shaft, and an elastic seal lip extending, over the resin seal lip, from an inner end of the elastic flanged portion in the axial direction of the rotation shaft toward the fluid to be sealed to surround the resin seal lip. The elastic seal lip incorporates a lip leading portion having a sealing surface which slidably and hermetically contacts the rotation shaft. The flanged portion and the elastic flanged portion are bonded and secured to each other while interposing at least one continuous bonded portion to continuously surround at least the rotation shaft, and the continuous bonded portion seals the joining surface between the flanged portion and the elastic flanged portion.

REFERENCE TO RELATED APPLICATIONS

This application is a continuation-in-part of prior U.S. patentapplication Ser. No. 07/645,442 filed on Jan. 24, 1991, now U.S. Pat.No. 5,183,271 issued on Feb. 2, 1993.

BACKGROUND OF THE INVENTION

The present invention relates to the sealing device utilized for aconstruction machine, a vehicle for civil construction engineering or anengine of an automobile and, more particularly, to a sealing deviceprovided with a seal lip made of resin material and a seal lip made ofrubber-like elastic material, which are firmly sealingly engaged witheach other, and also relates to a method of manufacturing the sealingdevice.

One example of conventional sealing devices will be described hereunderwith reference to FIGS. 10 and 11.

Referring to FIG. 10, a sealing device is generally designated byreference numeral 100. The sealing device 100 comprises a first sealring 103 provided with a seal lip 102 made of resin (hereinafter resinseal lip 102) hermetically contacting a rotating shaft 101 of amachinery such as a construction machine to which the sealing device isapplied, and a second seal ring 105 provided with a seal lip 104 made ofrubber-like elastic material (hereinafter rubber seal lip 104). Thesetwo seal rings 103 and 105 are in a tightly contacting relationship, butnot bonded to each other. To the second seal ring is bonded areinforcing ring 106 which are formed a plurality of holes 107 on thecircumferential portion thereof. The first seal ring 103 is providedwith a base portion 108 on which are formed a plurality of projections108a, which are engaged with the holes 107 of the reinforcing ring 106,for preventing the first seal ring from being rotated. An annular sealmember 109 made of a felt material is disposed on one side, i.e.,atmosphere side A of the second seal ring 105.

Before the application of the sealing device 100 to a housing 110 to besealed, the inner diameter of the rubber seal lip 104 is made smallerthan the outer diameter of the rotation shaft 101 in a state shown by adotted line in FIG. 10 for ensuring an interference fit, and the backsurface opposite the sealing surface by, of the resin lip 102 is inclose contact with the second seal ring 105. When the second seal ring105 is mounted, the rubber lip 104 is deformed as shown by a white arrowto thereby form a gap d between the back surface of the resin lip 102 ofthe first seal ring 103 and the second seal ring 105. An annular groove111 is formed in the sealing surface of the resin lip 102.

In the sealing device 100 of the structure described above, theatmosphere on the side A in FIG. 10 is sucked through the grooves 111 bypumping action during the rotation of the rotating shaft 101 and thesealing fluid B is thus sealed. When the shaft 101 is not rotated, thesealing fluid B is sealed by the rubber lip 104. During the describedoperation of the sealing device 100, once the first and second sealrings 103 and 105, as well as the first seal ring 103 and thereinforcing ring 106, are not connected, the resin lip 102 and therubber lip 104 of the first and second seal rings 103 and 105 are notinfluenced by each other, thus performing the sealing function.

In general, the sealing device of the structure described above may beformed in a formation mold, not shown, by heat compressing the firstseal ring 103 and rubber material and then carrying out thevulcanization treatment to thereby tightly secure the both materialswith relatively low cost.

However, with the sealing device 100 shown in FIG. 10, in a case wherethe sealing fluid B leaks on the side of the resin lip 102 by thelowering of the sealing performance due to the wearing or degradation ofthe rubber lip 104, the leaking fluid leaks on the side of theatmosphere A through the gap b, as shown by black arrows, between thecontacting surface of the second seal ring 105 and the base portion 108of the first seal ring 103 and the contacting surface of the baseportion 108 and the reinforcing ring 106.

In another example of a sealing device 200 shown in FIG. 11, the firstseal ring 202 provided with a resin lip 201 and the second seal ring 204provided with a rubber lip 203 are formed independently and, thereafter,the sealing device 200 is formed by caulking, as shown by a symbol R inFIG. 11, the outer periphery of a reinforcing ring 205 integrally formedwith the second seal ring 204.

According to this example, the leakage of the sealing fluid caused inthe aforementioned example is not caused because of the formation of thecaulked portion. However, it is obliged to additionally dispose areinforcing ring 206 for supporting the first ring 202 and, in addition,the caulking process is required for assembling the first seal ring 202and the second seal ring 204, thus increasing the manufacturing processand cost.

In a further example of the sealing device shown in FIG. 12, the sealingdevice 300 comprises a second seal ring 301 and a first seal ring 302closely contacting to the second ring 301 on the side of the atmosphereA. The second seal ring 301 includes a sealing body composed of anannular engaging portion 303, a flanged portion 304 and a rubber seallip 305 axially extending towards the sealing fluid side B and a metalring 306. The first seal ring 302 includes a flanged portion 307extending in a direction of the diameter of the rotation shaft and aresin seal lip 309 provided with a thread groove 308.

In the sealing device 300 of the structure described above, the rubberseal lip 305 and the resin seal lip are in close contact before themounting thereof as shown in solid outline in FIG. 12, but when both theseal lips are assembled in a portion between the housing 310 and therotation shaft 311, the seal lips 305 and 309 are elastically deformedin the diameter direction by amounts different from each other as shownby the dot and dash line (in the illustration, only the deformationamount of the seal lip 305 is shown), thereby achieving the sealingperformance therebetween. Accordingly, the first and second seal rings302 and 301 are in the state merely in contact with each other and theprojection 313 formed to a sealing body S is engaged with an engaginghole 312 formed to the flanged portion 307 of the first seal ring 302 tothereby attain the rotation prevention function between the respectiveseal rings 301 and 302.

FIG. 13 shows a still further example of the sealing device of the priorart and the sealing device 400 is of substantially the identicalstructure of the sealing device 300 shown in FIG. 12 except as describedbelow.

In the sealing device 400, an engaging hole 414 is formed in a metalring 406, and an engaging projection 415 formed to a second seal ring402 is engaged with the hole 414 to thereby attain the rotationprevention function between the first and second seal rings.

The other structures and the description thereof are eliminated hereinby increasing the reference numerals herein by 100 in FIG. 13 to thatapplied to portions or members corresponding to those shown in FIG. 12,for example, second seal ring 301 in FIG. 12 is increased in number toarrive at second seal ring 401 in FIG. 13.

In both the examples shown in FIGS. 12 and 13, the sealing device 300 or400 attains the sealing function for the sealing fluid B by sucking theatmosphere on the side A of the atmosphere by pumping function throughthe thread groove 308 or 408 during the rotation of the rotation shaft311 or 411. When the rotation of the rotation shaft stops, the sealingof the fluid B can be performed by the seal lip 305 or 405. The sealingdevices 300 or 400 are usually formed by a vulcanization treatment in aclosely contacting condition with a desired shape by heating andpressing the ring-shaped resin material, metal ring and rubber materialin a cavity of a mold, not shown.

However, with the sealing device 300 or 400 shown in FIGS. 12 or 13, ina case where the sealing fluid B leaks on the side of the resin lip 309or 409 by the lowering of the sealing performance due to the wearing ordegradation of the rubber lip 305 or 405, the leaking fluid leaks on theside of the atmosphere A through the gap d and the engaging hold 312 andthrough the contacting surface of the first seal ring 302 and the metalring 306 (FIG. 12), and through the outer peripheral side of the firstseal ring 402 and the engaging hole 414 (FIG. 13).

In addition, according to these examples, it is necessary to form thefirst seal ring before the vulcanization treatment so as to have anL-shaped cross section at the manufacturing of the sealing device.Furthermore, the engaging hold 312 of the first seal ring 302 and theengaging hole 414 of the metal ring 406 are additionally required forthe manufacture of the sealing devices 300 or 400, thus beingtroublesome and involving increased manufacturing cost.

SUMMARY OF THE INVENTION

An object of the present invention is to substantially eliminate defectsor drawbacks encountered in the prior art and to provide a sealingdevice and a method of manufacturing of the same capable of achieving animproved sealing function effectively preventing a sealing fluid fromleaking outward.

This and other objects can be achieved in one aspect by providing asealing device disposed between two members which are relativelyrotatable, comprising a first seal ring provided with a resin seal lipbeing disposed in an axial direction of one of the members to be sealedand having a first sealing surface, a second seal ring provided with anelastic rubber seal lip disposed in an axial direction of one of themembers to be sealed, the rubber seal lip being provided with a sealingsurface closely contacting to the sealing surface of the resin seal lip,and means for firmly securing the first and second seal rings.

In preferred embodiments, the means for securing the first and secondseal rings is composed of an annular sealing recess formed on anothersurface of the resin seal lip opposed to the sealing surface thereof anda sealing projection formed on the sealing surface of the rubber seallip of the second seal ring.

The first and second seal rings further include flanged portionsrespectively extending from base portions of the resin and rubber seallips in a diameter direction of one of the members to be sealed, theflanged portion of the first seal ring having an end surface facinganother one of members to be sealed and the means for securing the firstand second seal rings is composed of a bonding agent disposed betweenthe end face of the first seal ring and the flanged portion of thesecond seal ring.

In another aspect according to the present invention, there is provideda method of manufacturing a sealing device by utilizing a mold having aninner cavity, comprising the steps of preparing a ring member and anannular resin material having an L-shaped section including acylindrical portion provided with an annular recess and a flangedportion, disposing the ring member and the annular resin material in thecavity of the mold in a laminated state, disposing a rubber material onthe laminated ring member and the annular resin material, and heatingand pressuring the ring member, the resin material and the rubbermaterial disposed in the cavity to thereby carry out a vulcanizationtreatment so as to form a projection with a vulcanized rubber material,the projection having an outer shape corresponding to an inner shape ofthe annular recess.

In a further aspect of the present invention, there is provided a methodof manufacturing a sealing device by utilizing a mold having an innercavity, comprising the steps of preparing a ring member and an annularresin material having an L-shaped section including a cylindricalportion provided with an annular recess and a flanged portion, disposingthe ring member and the annular resin material in the cavity of the moldin a laminated state, disposing a rubber material on the laminated ringmember and the annular resin material, heating and pressurizing the ringmember, the resin material and the rubber material disposed in thecavity to thereby carry out a vulcanization treatment, and applying abonding agent to an end surface of the flanged portion.

According to the sealing devices and the manufacturing methods thereofof the character described above, in one aspect, the first seal ringprovided with the resin seal lip and the second seal ring provided withthe rubber seal lip are firmly sealingly engaged by engaging the sealingrecess formed to the resin seal lip with the sealing projection formedto the rubber seal lip. The projection is formed at the same time of thevulcanization treatment of the second seal ring.

In another aspect, the resin seal lip and the rubber seal lip areclosely seal contacted with a small gap between the sealing surfaces ofboth the seal lips. However, the end surface of the flanged portion ofthe first seal ring is bonded to the second seal ring, i.e. the metalring or heated and fluidized rubber material, at the same time of thevulcanization treatment.

BRIEF DESCRIPTION OF THE DRAWINGS

In the accompanying drawings:

FIG. 1 is a sectional view of a half portion of a first embodiment of asealing device, before the mounting to a machinery to be sealed,according to the present invention;

FIG. 2 is an enlarged view of a cutout groove of a resin seal lip of thesealing device shown in FIG. 1;

FIG. 3 is a portion of the sealing device shown in FIG. 1 after themounting thereof;

FIG. 4 represents an embodiment for manufacturing the sealing device ofFIG. 1 in which the device is in the state before the vulcanizationtreatment with a mold being opened;

FIG. 5 shows a mold closing state at the vulcanization treatment;

FIG. 6 is a sectional view similar to that of FIG. 1 showing a sealingdevice of a second embodiment according to the present invention;

FIGS. 7A and 7B respectively share steps in the pretreatment of a resinroll;

FIGS. 8 and 9 are views similar to those of FIGS. 4 and 5 with referenceto the second embodiment;

FIGS. 10 to 13 are views similar to those of FIGS. 1 and 6 of sealingdevices according to the prior art;

FIG. 14 is a sealing device according to another embodiment of thepresent invention, similar to FIG. 1;

FIG. 15 is a perspective view of a first seal ring of the sealing deviceshown in FIG. 14;

FIGS. 16A, 16B, and 16C illustrate three steps in producing a secondseal ring for an embodiment of the sealing device according to thepresent invention;

FIGS. 17A, 17B, 17C, and 17D illustrate four steps in forming anintermediately molded resin member according to the present invention;and

FIG. 18 illustrates application of adhesive to an outer extremitysurface of the intermediately-molded resin member formed by the steps inFIGS. 17A-17D.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

A first embodiment of a sealing device according to the presentinvention is first described with reference to FIGS. 1 to 5, in whichFIG. 1 shows a sectional view of a half portion of a sealing device 1before the mounting to machinery or mechanism to be sealed. The sealingdevice 1 is utilized by mounting the same between a housing 2 and arotatable shaft 3 of the mechanism to be sealed. The sealing device 1 iscomposed of, by tightly securing, a first seal ring 6, totally made of aresin material such as ethylene tetrafluoride resin, comprising a resinseal lip 4 having substantially an L-shaped section and extending in anaxial direction of the shaft 3 and a base portion 5 extending in adirection of a diameter of the shaft 3 and composed of a second sealring 10, totally made of a rubber material, comprising a rubber elasticlip 7, a flanged portion extending in the direction of the diameter ofthe shaft 3 and a fitting portion 9. The first seal ring 6 is positionedon the side of the atmosphere A so as to support the atmospheric sidesurface of the second seal ring 10. A reinforcing ring 11 is formedintegrally with the second seal ring 10. The first and second seal rings6 and 10 are disposed in a contact state as well as the first seal ring6 and the reinforcing ring 11. The reinforcing ring 11 is provided withan inward flanged portion 11a having a circumferential surface in whicha plurality of engaging holes 12 are formed, only one hole beingillustrated in FIG. 1 for the sake of convenience. Annularly spacedprojections 13 are formed on the base portion 5 of the first seal ring 6and the projections 13 are engaged with the holes 12 to thereby preventthe first seal ring 6 from being rotated. An annular sealing member 14made of felt, for example, is disposed on the atmospheric side surfaceof the second seal ring 10.

The sealing device 1, before the mounting in the housing 2, since theinner diameter of the rubber lip 7 of the second ring 10 is made smallerthan the outer diameter of the rotation shaft 10 so as to maintain aninterference fit, the back surface (opposite to the sealing surface D,i.e. the sliding surface) of the resin lip 4 is in close contact withthe second seal ring 10. After the mounting of the sealing device 1 inthe housing 2, the rubber lip 7 is elastically deformed as shown by awhite arrow to thereby form a gap E between the rubber lip 7 and theresin lip 4, as shown in FIG. 3. A thread groove 15 is formed in thesealing surface D of the resin lip 4. At least one sharp annular cutoutgroove 16 is formed on the back surface of the resin lip 4 as an annularsealing recess. The groove 16 may be formed in a spiral shape. As shownin FIG. 2, the cutout groove 16 is formed so as to have an angularrelationship of α>β, as shown in FIG. 2 in an enlarged scale, in whichthe symbol α designates an angle on the atmosphere side A and the symbolβ is an angle on the side of the sealing fluid B with a boundary of aline normal to the rotation shaft 3. At least one annular projection 17in shape of a wedge in section is formed on the surface in close contactwith the rear surface of the resin lip 4 as a sealing protrusion.

The sealing device 1 of the structure described above is operated asfollows.

The atmosphere A is sucked along the thread groove 15 by the pumpingfunction during the rotation of the rotation shaft 3 to thereby seal thesealing fluid B. On the other hand, when the rotation shaft 3 stops, thesealing fluid B is sealed by the rubber lip 7. In this state, the firstand second seal rings 6 and 10 are not in close contact with each other,as well as the first seal ring 6 and the reinforcing ring 11, so thatthe resin lip 4 and the rubber lip 7 are not in interfering relationshipwith each other, thus attaining the sealing performance respectively.

During the sealing operation described above, as shown in FIG. 3, theannular projection 17 is in close contact with the inclining surface onthe side of the sealing fluid B of the annular cutout groove 16 tothereby seal the gap E, so that there is no leak on the atmosphere sideA through the gap E and the contacting surface between the reinforcingring 11 and the first seal ring 6 even if the sealing fluid leaksthrough the sealing surface due to the wearing or degradation of therubber lip 7.

The sealing device 1 of the first embodiment of the described charactercan be manufactured in the following manner.

The sealing device 1 is manufactured by using a mold assembly 20 of thetype shown in FIG. 4. The mold 20 comprises upper and lower mold halves23 and 22, and the lower mold half 22 includes a first molding member 25for forming a bottom portion, a second molding member 26 for forming awall portion of the inner diameter side and a core molding member 27. Amale thread 28 is formed on the outer periphery of the core moldingmember 27.

The upper mold half 23 is provided with a lower surface on which isformed an annular projection 29 to be inserted into the lower mold half22. When both the mold halves 22 and 23 are closed, an annular cavity 21having a shape corresponding to the second seal ring 10 is definedbetween the projection 29 and the lower mold half 22.

In the next step, the reinforcing ring 11 and a ring-shaped resinmaterial F for forming the first seal ring 6 are preliminarily moldedbefore the vulcanization of the second seal ring 10. The resin materialF has an L-shaped section and is provided with a cylindrical portion F'having an outer periphery in which the cutout groove 16 is preliminarilyformed. The engaging holes 12 are formed to the inward flanged portion11a of the reinforcing ring 11 along the circumferential directionthereof. The reinforcing ring 11 and the resin material F of thecharacter described above are disposed in the laminated state in theopened mold cavity 21.

A rubber material, not shown, is further disposed in the mold 20, whichis then closed. Under this condition, the heating and pressing processesare carried out. According to these processes, the cylindrical portionF' of the resin material F softened by the heat is forced against thesurface of the core molding member 27 as shown by small arrows shown inFIG. 5, whereby the thread groove 15 having a shape corresponding tothat of the male thread 28 formed on the surface of the core moldingmember 27 is formed on the inner peripheral surface of the cylindricalportion F'. At the same time, the projections 17 having a shapecorresponding to that of the annular cutout groove 16 is vulcanized onthe rubber material G closely contacting to the outer periphery of thecylindrical portion F'. Furthermore, the resin material is caused tointrude into the engaging hole 12 to thereby form the projection 13,thus realizing the firm and close sealing condition between the rubbermaterial G and the resin material F.

After the vulcanization process, a mold product is taken out by openingthe mold assembly and any excessive portion extending from the rubberlip 7 of the mold product is properly cut away, thus completing themanufacturing of the sealing device 1.

According to the first embodiment of the present invention, the annularcutout groove 16 corresponding to the annular projection 17 can beformed easily with reduced processing effort on the surface of thesecond seal ring 10 contacting the first seal ring 6.

In a preferred modification, as shown in FIG. 1, annular grooves T maybe formed on the surface of the resin seal ring contacting to thesurface of the rubber seal ring for effectively preventing the fluidfrom leaking inside the sealing device.

A second embodiment of the sealing device according to the presentinvention will be described hereunder with reference to FIGS. 6 to 9.

Referring to FIG. 6, a sealing device is designated by reference numeral50 which is in a state before the mounting between a rotation shaft 52and a housing 53 to be sealed. The sealing device 50 comprises a seconddeal ring 54 disposed on the sealing fluid side B and a first sealingring 55 tightly contacting the atmospheric side surface A of the secondseal ring 54.

The second seal ring 54 is composed of a sealing body 56 made of arubber material and a metal ring 57 sintered to the sealing body 56, andthe sealing body 56 comprises a seal lip 58 extending axially of therotation shaft 52 to be sealed, an outward flanged portion 59 extendingfrom a base portion of the seal lip 58 towards the housing 53 and anengaging portion 60 to be tightly contacted to the housing 53. The innerdiameter of the seal lip 58 is made smaller than the outer diameter ofthe rotation shaft 52 to be sealed. The metal ring 57 is molded to be inan L-shape in section so as to have a cylindrical base portion 61 and aninward flanged portion 62 and the base portion 61 has a diameter largerthan that of the first seal ring 55.

The first seal ring 55 is made of a resin material such as ethylenetetrafluoride resin so as to have an L-shaped section and is composed ofa seal lip 63 extending axially of the rotation shaft 52 to be sealedand an outward flanged portion 54 extending from the base portion of theseal lip 63 towards the housing 53. A thread groove 65 is formed on theinner peripheral surface of the seal lip 63, and the inner diameter ofthe seal lip 63 is made smaller than the outer diameter of the rotationshaft 52 to be sealed. The seal lip 63 and the flanged portion 64 of thesecond seal ring 55 thus formed are closely contacted to the seal lip 58and the flanged portion 59 of the second seal ring 54, respectively. Theouter peripheral side end surface H on the housing side of the flangedportion 64 of the first seal ring 55 is fixedly bonded to the engagingportion 60 of the second seal ring 54 by bonding means such as a bondingagent.

When the sealing device 50 of the structure described above is mountedbetween the rotation shaft 52 and the housing 53 of machinery or thelike to be sealed, the seal lips 58 and 63 are deformed in the radialdirection of the rotation shaft 52 by the amounts different from eachother and seal the rotation shaft 52 due to a predeterminedinterference. In the illustration of FIG. 6, only the deformation of theseal lip 58 is shown by dot and dash line because the seal lip 58 isdeformed by the amount larger than that of the seal lip 63. Therefore, agap K is caused between the seal lips 58 and 63.

The operation of the sealing device 50 of the character described aboveis as follows.

The atmosphere A is sucked along the threaded groove 65 by the pumpingfunction during the rotation of the rotation shaft 52 to thereby sealthe sealing fluid B. On the other hand, when the rotation shaft 52stops, the sealing fluid B is sealed by the rubber seal lip 58. In thisstate, since the end surface H of the flanged portion 64 of the firstseal ring 54 is bonded to the engaging portion 60 of the second sealring 54, the sealing effect can be performed even if the sealing fluid Bintrudes into the gap K through the sealing surface of the rotationshaft 52 due to the degradation, for example, of the seal lip 58, thuspreventing the sealing fluid B from leaking in the atmospheric side Aand hence attaining the sealing performance effectively.

In addition, the bonding performed between the end surface H of theflanged portion 64 extending in the diameter direction and the engagingportion 60 does not adversely affect on the elastic deformation of theseal lips 58 and 63 which is carried out for the ensurance of theinterference. In a modification, the flanged portion 64 may be furtherextended towards the housing 53 and may be bonded to the base portion 61of the metal ring 57.

The sealing device 50 of this embodiment will be manufactured in thefollowing manner.

Referring first to FIG. 7, a resin roll 66 is first prepared and a metalnatrium (sodium), for example, is applied on the outer peripheralsurface 67 of the resin roll 66 to make coarse the surface 67 toincrease the surface area. A bonding agent 68 is thereafter coated onthe metal natrium surface with a predetermined thickness. The resin roll66 is cut with a predetermined thickness as shown in FIG. 7B. As show inFIG. 8, the cut resin roll is thereafter worked to form a resin material71 provided with a cylindrical portion 69 and an outward flanged portion70 extending in a diameter direction thereof from one end of thecylindrical portion 69. The end surface H of the flanged portion 70 iscoated with the bonding agent 68. There is also prepared a metal ring 57having a diameter larger than that of the resin material 71. The metalring 57 and the resin material 71 are disposed in a cavity 73 of a mold72, which is composed of lower and upper, as viewed, mold halves 74 and75. The lower mold half 74 is composed of a first molding member 75aforming the bottom surface of the sealing device, a second moldingmember 76 for forming an outer diameter side wall surface and a coremolding member 77. On the outer peripheral surface of the core moldingmember 77 is formed a male thread 78.

On the lower surface of the upper mold half 75 is formed an annularprojection 79 to be inserted into the lower mold half 74 so that theannular cavity 73 is defined between the projection 79 and the lowermold half 74 when the mold 72 is closed.

The vulcanization treatment of the sealing device 50 is carried out inaccordance with the following manner.

First, a rubber material, not shown, is positioned in the cavity 73 andthe mold 72 is then closed. Heating and press-rising treatments arethereafter performed. A rubber 80 fluidized as shown in FIG. 9 flows inthe cavity 73 along the surfaces of the cylindrical portion 69 and theflanged portion of the resin material 71. The cylindrical portion 69softened by the heat treatment is forced against, as shown by arrows,the surface of the core molding member 77 by the pressure of thefluidized rubber 80, whereby a thread groove 65 having a shapecorresponding to the male thread 78 formed on the surface of the coremolding member 78 is formed on the inner peripheral surface of thecylindrical portion 69 of the resin material 71.

Substantially at the same time, the rubber 80 is bonded to the endsurface H of the flanged portion 70 of the resin material 71.

After the vulcanization process, a mold product is taken out from themold 72 and the excess portion of the rubber 80 is cut away, thusforming the sealing device 50. When the mold product is taken out fromthe mold 72, the resin material 71, i.e. the seal lip 63 of the firstseal ring 55, is deformed in a direction of the inner diameter thereofby the replacing force thereof, thus ensuring the interference at themounting time of the sealing device into the housing 53.

According to this embodiment, since the bonding between the rubber 80and the end surface H of the resin material 71 is performed at the sametime as the vulcanization treatment, thus removing a process for formingthe engaging hole.

The resin material 71 may be bonded to the metal ring 57 by enlargingthe diameter of the flanged portion 70 thereof.

Furthermore, in the illustrated embodiment, the sealing device 50 issecured to the housing side 53 and the seal lips 58 and 63 are closelycontacted to the rotation shaft 52, but in an alternation, the sealingdevice 50 may be secured to the rotation shaft side 52 and the seal lips58 and 63 may be closely contacted to the housing 53.

FIG. 14 is a sealing device according to another embodiment of thepresent invention.

The sealing device according to this embodiment comprises a first sealring 154 made of resin and a second seal ring 155 made of rubber-likeelastic material, the first seal ring 154 and the second seal ring 155being annular members disposed in a gap present between the innersurface of a housing 153 and the outer surface of a rotation shaft 152which is coaxially and relatively rotatively fastened with respect tothe housing 153.

The first seal ring 154 comprises a resin flanged portion 164 formedinto a washer-like shape to surround the rotation shaft 152 andextending in a direction of the radius of the rotation shaft 152, thefirst seal ring 154 further comprising a resin seal lip 163 formed intoa cylinder-like shape extending from the inner extremity of the resinflanged portion 164 in an axial direction of the rotation shaft 152. Theinner surface of the resin seal lip 163 is slidably disposed inhermetically contact with the outer surface of the rotation shaft 152. Athread groove 163a is formed in the surface of the resin seal lip 163which slides on the rotation shaft 152, the thread groove 163a having apumping function, so that a sealing effect is improved.

On the other hand, the second seal ring 155 comprises a rubber-likeelastic flanged portion 159 formed into a washer-like shape, made of arubber-like elastic material reinforced by a reinforcing ring 157 andextending in a direction of the radius of the rotation shaft 152, thesecond seal ring 155 further comprising a rubber-like elastic seal lip158 extending from the inner extremity of the rubber-like elasticflanged portion 159.

The reinforcing ring 157 is a metal annular member having an L-shapedcross sectional shape and comprising an outer cylindrical portion 161integrally embedded with the outer fitting portion 156, the reinforcingring 157 further comprising a metal flanged portion 162 extending fromthe extremity of the atmospheric side of the outer cylindrical portion161 in a direction of the radius of the rotation shaft 152. The metalflanged portion 162 supports the surface of the resin flanged portion164 of the first seal ring 154 adjacent to the atmosphere. The metalflanged portion 162 and the resin flanged portion 164 are laminated.Therefore, the rubber-like elastic flanged portion 159, the resinflanged portion 164 and the metal flanged portion 162 are stackedsequentially in a direction from fluid B to be scaled toward atmosphereA.

The rubber-like elastic seal lip 158 is disposed to surround the resinseal lip 163 while being positioned in contact in the direction of withthe outer surface of the resin seal lip 163. A lip extremity 158a of therubber-like elastic seal lip 158 extends t the fluid B to be sealedafter it has exceeded the leading portion of the resin seal lip 163.Also a thread groove 158b having the pumping function is formed in thesliding surface of the lip extremity 158a. Furthermore, a spring 158cfor causing the rubber-like elastic seal lip 158 to attain clampingforce is fastened to the lip extremity 158a.

The fluid B is sealed doubly by the rubber-like elastic seal lip 158 andthe resin seal lip 163.

The pressure of the seal fluid acting on the rubber-like elastic seallip 158 is maintained by the resin seal lip 163, so that an excessiveincrease in the sliding resistance of the lip extremity 158a of therubber-like elastic seal lip 158 and proceeding of abrasion under highpressure are prevented.

Although the rubber-like elastic seal lip 158 extends along the backsurface of the resin seal lip 163, they are separated from each other soas to be capable of individually moving, so that the rubber-like elasticseal lip 163 is able to follow small projections and pits of the surfaceof the rotation shaft 152 and the small irregular movement of the same.

On the other hand, the resin flanged portion 164 and the rubber-likeelastic flanged portion 159 are secured to each other by bonding. Thebonded region has a continuous bonded portion H which continuouslysurrounds at least the rotation shaft 152. By virtue of the continuousbonded portion H, leakage of the sealed fluid passing through a portionbetween the joined surfaces of the resin seal lip 163 and therubber-like elastic seal lip 158 is prevented.

In the illustrated embodiment, the continuous bonded portion H is formedon the outer extremity surface 164a is tapered in a direction alongwhich its diameter is reduced toward the fluid B to be sealed, so that acontact area with a rubber-like elastic member 160 is enlarged andtherefore bonding can be performed assuredly.

The position, to which the continuous bonded portion H is formed, is notlimited to the outer extremity surface 164a of the resin flanged portion164. The continuous bonded portion H may, as shown in FIG. 15, beenlarged to a region in the vicinity of the outer extremity surface164a, or the same is formed in a portion except for the outer extremitysurface 164a. In short, it may be disposed at an arbitrary position in arange (hatched portion on FIG. 15) in which the resin flanged portion164 comes in contact with the rubber-like elastic flanged portion 159.However, it is preferable that the continuous bonded portion H be notformed adjacent to the inner extremity of the resin flanged portion 164but be formed adjacent to the outer extremity of the same in order torealize excellent following characteristics of the rubber-like elasticseal lip 158. An area shown by two dots and chain line is an area notbonded.

As an alternative to forming one continuous bonded portion H, aplurality of continuous bonded portions H may be formed from the innerextremity adjacent to the resin seal lip 163 to the outer extremity tosurround it several times. As a result, reliability can be improvedbecause a leakage from sealing taken place in a portion of thecontinuous bonded portion H can be sealed by another portion of thecontinuous bonded portion H.

As an alternative to partially forming the continuous bonded portion H,the overall contact surface may be bonded.

The contact surfaces of the resin flanged portion 164 and the metalflanged portion 162 may be bonded to each other, or may be freed frombonding. In the case where a continuous bonded portion similarly to theresin flanged portion 164 and the rubber-like elastic flanged portion159 is formed between the resin flanged portion 164 and the metalflanged portion 162, the sealing performance can further be improved.

On the other hand, a dust seal member 190 is, by bonding secured to thesurface of the metal flanged portion 162 adjacent to the atmosphere inorder to prevent undesirable introduction of dust. The dust seal member190 is manufactured by forming a cloth such as non-woven fabric or thelike into a washer-like shape, the dust seal member 190 having an innerextremity which slidably comes in contact with the rotation shaft 152.Though not shown, the resin flanged portion 164 bites a hole 162a of themetal flanged portion 162 to be surely secured.

FIGS. 16 to 18 illustrate a method of manufacturing the sealing devicethus structured.

The sealing device according to this embodiment is basicallymanufactured by integrally molding the resin first seal ring 154 made ofthe resin and the second seal ring 155 made of the rubber-like elasticmaterial by using a mold.

Prior to performing the molding process, an intermediately-molded resinmember 165 having an intermediate shape, which will be formed into thefirst seal ring 154, is formed. The intermediately-molded resin member165 is formed into a bevel washer shape having the inner extremity whichwill be formed into the resin seal lip 163 and the outer extremity whichwill be formed into the resin flanged portion. The aforesaid innerextremity has two chamfers 155a and 155b.

The aforesaid intermediately molded resin member 165 as shown in FIGS.17C and 17D is formed, while having a predetermined thickness, bycutting an end surface 166a of a raw resin material 166 formed into acylinder having a thick wall. For example, it can easily be formed bycutting the raw resin material 166, which is being rotated around itscentral axis, by using a knife 167.

Chamfered portions 165b and 165c formed at the inner extremities of theintermediately-molded resin member 165 may be formed after theintermediately-molded resin member 165 has been obtained by cutting. Asan alternative to this, it may be obtained by cutting as described aboveafter the inner extremities of conical end surface 166a of the raw resinmaterial 166 have been chambered by means of a knife or bite 168 asshown in FIGS. 17A and 17B.

Then, an adhesive is applied to an outer extremity surface 165a of theintermediately-molded resin member 165 thus molded as shown in FIG. 18,the adhesive being applied continuously along the circumference. Theapplied adhesive is able to overflow into the two side surface of theintermediately-molded resin member 165 over the outer extremity surface165a as well as the outer extremity surface 165a of the same. Since theadhesion of the adhesive to the inner surface of theintermediately-molded resin member 165 causes the resin seal lip 163 andthe rubber-like elastic seal lip 158 to be undesirably bonded to eachother at the time of the molding process, an allowable range L, which isnot affected by the adhesive, is determined. The allowable range Lcorresponds to a portion of the outer surface of theintermediately-molded resin member 165 which will be formed into theresin flanged portion 164 after the molding process is completed.

Since the continuous bonded portion H is not limited to the outerextremity surface 164a of the resin flanged portion 164 but the same maybe formed at an arbitrary position of the contact surface between theresin flanged portion 164 and the rubber-like elastic flanged portion159 as described above, the position of the application is determined tocorrespond to the position of the continuous bonded portion.

As for the adhesive, an optimum adhesive is selected to be adaptable tothe employed resin material which constitutes the first seal ring 154and the employed rubber-like elastic material which constitutes thesecond seal ring 155. If necessary, surface treatment is applied priorto applying the adhesive. In the case where PTFE(polytetrafluoroethylene) is employed as the resin material, the surfaceis applied with a metal sodium treatment to be activated because thePTFE has unsatisfactory adhesivity. However, bonding can be performedwhile eliminating the necessity of using the adhesive depending upon thematerial, because the adhesive is selected depending upon the materialrelationship between the resin material and the rubber-like elasticmaterial. In the case of a certain type of rubber material, a bondedstate can be realized only by subjecting the surface of theintermediately-molded resin member 165 to the metal sodium treatment.

The intermediately-molded resin member 165 is, together with thereinforcing ring 157 and a rubber material 180 to be molded, insertedinto an opened mold 172, and it is, together with the rubber-likeelastic seal ring 154, molded.

The mold 172 will now be described. The mold 172 is basically composedof an upper mold half 175 and a lower mold half 173 as shown in FIGS.16A, 16B, and 16C. The lower mold half 173 has an annular recess 173aopened upwards, so that a sealed cavity is formed by closing the annularrecess 173a by the upper mold half 175 when the two mold halves areclosed.

The lower mold half 173 is composed of a first mold 174 whichconstitutes the bottom surface of the annular recess 173a, a second mold176 serving as an intermediate mold which is placed on the first mold174 and which constitutes the outer wall surface of the annular recess173a, and a core 177 which is inserted into a hole 174a formed at thecentral portion of the first mold 174 and which constitutes the innerwall surface of the annular recess 173a. A transferring thread groove178 having a profile obtainable by inverting the profile of the threadgroove 163a to be formed in the resin seal lip 163 is formed in theouter surface of the core 177 which faces the annular recess 173a.

The molding process is performed as follows:

First, as shown in FIG. 16A, the reinforcing ring 157 and theintermediately-molded resin member 165 are inserted into the annularrecess 173a of the lower mold half 173. The reinforcing ring 157 isinserted while causing its metal flanged portion 162 to face downwards,so that the metal flanged portion 162 is placed on the bottom surface ofthe annular recess 173a. Then, the outer extremity of theintermediately-molded resin member 165 is inserted into the annularrecess 173a while being faced downwards. As a result, the outerextremity of the intermediately-molded resin member 165 comes in contactwith the upper surface of the metal flanged portion 162 of thereinforcing ring 157 on the corner of the metal flanged portion 162 andthe outer cylindrical portion 161. On the other hand, the innerextremity of the intermediately-molded resin member 165 is positioned onthe top end of the core 177. It is preferable that the inner diameter ofthe intermediately-molded resin member 165 be substantially the same orsmaller than the outer diameter of the core 177.

Then, as shown in FIG. 16B, the bottom-most portion of which is shown inan enlarged view in FIG. 16C, the raw rubber material 180 is heated andpressurized, and the cavity is filled with the fluidized raw rubbermaterial 180, so that the second seal ring 155 having a predeterminedshape is molded. The central portion of the intermediately-molded resinmember 165, which has been plasticized due to heat applied at the timeof clamping the molds, is bent into an L-shape due to the moldingpressure of the raw rubber material 180, while its inner surface ispressed by the surface of the core 177, so that the resin seal lip 163is molded. On the other hand, the outer surface of the same is pressedby the metal flanged portion 162, so that the resin flanged portion 164is molded. Furthermore, the profile of the transferring thread groove178 formed in the outer surface of the core is transferred to the innersurface of the resin seal lip 163.

Moreover, since the outer extremity surface 165a of theintermediately-molded resin member 165 is formed to provide a taperedsurface, a V-shaped gap is caused between the reinforcing ring 157 andthe outer cylindrical portion 161 as shown in FIG. 16C. The rubber-likematerial which invades this gap is forcibly pressed against the outerextremity surface 165a of the intermediately-molded resin member 165 bywedging action. Accordingly, it is extremely effective to utilize theouter extremity surface 165a as a surface to be bonded.

After the fluidized raw rubber material 180 has been hardened, the moldis opened so as to separate the molded product, so that the desiredsealing device is manufactured by performing post-treatments such as aprocess of removing burrs undesirably formed on the leading portion ofthe rubber-like elastic seal lip 163.

Although omitted from illustration, a thread groove 163a formed in asurface of the rubber-like elastic seal lip 163 may be formed by amolding process performed in such a manner that a transferring threadgroove is, in the surface of the core 177 of the mold 172, formed tohave a profile obtainable by inverting the profile of the thread groove163b. As an alternative to this, it may be formed by machining to beperformed after the molding process has been completed.

It is to be understood that the present invention is not limited to thedescribed embodiments and many other changes and modifications may bemade without departing from the scope of the appended claims.

What is claimed is:
 1. A method of molding a sealing device by using amold having an inner cavity, comprising the steps of:preparing a resinmaterial having a cylindrical shape; cutting the resin material to cutoff a conical washer member; chamfering an inner end portion of the cutconical washer member; disposing the conical washer member in the cavityof the mold; preparing an elastic material to be supplied in the cavityof the mold; supplying the elastic material on the conical washer memberin the mold; pressuring the conical washer member and the suppliedelastic material to fluidize the elastic material so that the cavity ofthe mold is filled up with the fluidized elastic material in apredetermined shape which includes a flanged portion; and deforming theconical washer member to have an L-shaped cross section by utilizing thepressure of the fluidized elastic material, so that an outer extreme endportion of the conical washer member provides a conical outer peripheryhaving a predetermined inclination in the cavity with respect to saidflanged portion.
 2. A method according to claim 1, further comprising astep of applying a bonding agent on the outer periphery of the conicalwasher member before the elastic material is disposed thereon.